I wanted to write fizzbuzz, but instead of just printing, store it in an array.

The problem is converting the numbers to strings. I first tried with bufPrint, but It outputed white-space instead of a number. Then I tried out with allocPrint, it compiles the app, but after entering the number crashes, with weird error messages in std/fmt. I tried printing the output of allocPrint, it outputs correctly, but I can't add it to the array.

After much more, I found out that the type that allocPrint produces is a string of type []u8, but my type is []const u8. How can I turn the output of the function to []const u8?

The askUser function works correctly & produces a u64, the problem is not related to it. Also, what is the best or most common string type in zig?

code

const std = @import("std");

fn fizzBuzz(x: usize) !std.ArrayListAligned([]const u8, null) {
    const allocator = std.heap.page_allocator;

    var array = std.ArrayList([]const u8).init(allocator);

    var i: usize = 0;
    while (i != x) : (i  = 1) {
        const string = try std.fmt.allocPrint(allocator, "{d}", .{i   1});
        defer allocator.free(string);

        try array.append(if (((i   1) % 3 == 0) and ((i   1) % 5 == 0)) "FizzBuzz"
            else if ((i   1) % 3 == 0) "Fizz"
            else if ((i   1) % 5 == 0) "Buzz" else string);
    }

    return array;
}

pub fn main() !void {
    const count = try askUser("! ");
    var x = try fizzBuzz(@intCast(usize, count));
    defer x.deinit();

    defer std.debug.print("\n", .{});
    for (x.items) |y| {
        std.debug.print("{s} ", .{y});
    }
}

CodePudding user response：

The std.ArrayList([]const u8) doesn't take ownership of the strings you put into it. It only takes slices (which is a pointer length). So, when you deallocate the strings in the loop you invalidate the slices that you just added into the array list.
Simply removing defer allocator.free(string); makes your program print a correct result.

How to convert []u8 to []const u8 in Zig?

No need to do anything, the type coercion happens implicitly.